For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
A young peasant named Julien Sorel gets a job as a tutor for the children of his town's mayor. He soon begins an affair with the mayor's wife. Word about the affair spreads through the town and Julien runs away to a seminary school (for priests) to avoid scandal. He slogs his way through this school before getting offered another job as a personal secretary for a wealthy man in Paris named the Marquis de La Mole.
Act II
Julien travels to Paris and becomes a part of the de La Mole household. He's somewhat invisible to the upper class people of Paris because they know he's just a peasant. Over time, he takes on a fake backstory to make people think he's from a wealthy family. He also starts a romantic relationship with the Marquis' daughter, Mathilde. Mathilde gets pregnant and they decide to get married. The Marquis objects at first, but then just gives Julien all the money and status he needs to be worthy of Mathilde. Everything looks great. Julien has the girl he loves and all the status and power he could ever want.
Act III
Julien's plan to marry Mathilde goes south when the Marquis de La Mole receives a letter from Julien's old lover, Madame de Rênal, saying that Julien is just a social climber who wants to marry Mathilde for her money. The Marquis rejects Julien. Julien travels back to his hometown and shoots Madame de Rênal in church. He is convicted of attempted murder (she survives) and sentenced to death. People try to convince him to appeal the decision, but he's too weary with the hypocrisy and shallowness of French society to go on living. He gets beheaded and the story ends.